Whatever we do will be risky – but something has to happen soon as the terrorists gain power, ground, weapons and swell their £100billion war chest daily.

Here we examine our options.

Strike a deal with Syria’s President Bashar Assad

The UK funded and trained the Free Syrian Army to fight his regime but many defected to al-Qaeda and then IS.

For: An alliance with Assad would put huge pressure on IS, whose main source of income is stolen Syrian oil. IS would soon be eradicated if oil was defended.

Against: The pact would embolden Assad, whose regime has used chemical and biological weapons against civilians and committed human rights abuses.

Send in special forces to rescue the hostages and hit IS gunmen

The SAS already has troops on the ground in Iraq pin-pointing drop-zones for US and UK to supply food and water to refugees. But they are not currently on a combat mission.

For: The SAS are the best hostage rescue troops in the world and could also kill the maniacs who have seized innocents. They could also strike against IS and call in air support to bomb the IS hierarchy.

Against: Unless the SAS has detailed intelligence on buildings hostages are being held in, the risk of failure – as already proved by an earlier American Delta force mission – is too high.

Back US air strikes by with RAF Tornados

Bombing sorties to help smash IS supply lines and kill IS gunmen and key players.

For: No boots on the ground means a low risk of servicemen being captured while offering maximum returns in obliterating large sections of IS fighters.

Against: Air strikes require special forces on the ground to identify targets. If an SAS man was caught it would be a massive coup for the militants.

Encourage regional powers to take out IS

Turkey, Saudi and Qatar are helping various Syrian rebel groups, even IS. Iran and Russia are aiding Assad’s forces. In Iraq, Iran is funding Shia militia against IS while Saudi spooks finance fellow Sunnis IS.

For: Distances Britain from overt and costly involvement in war, reducing tension at home and lowering the risk of domestic terror attacks.

Against: Iran and Russia could use situation to back Assad further and gain a greater foothold in the Middle East.

Launch a ground attack against IS, backed by Iraqi and Kurdish Peshmerga.

A strong option as proved by the Iraq invasion of 2003 when our well-trained troops fought effectively in the desert.

For: A decisive move that would destroy IS and re-establish security to the region, whilst warning to other extremists that the west will not be cowed.

Against: David Cameron knows sending British troops into battle against IS would cost hundreds of lives. His credibility would be battered in the run-up to next year’s election and it would cost billions.

Ignore IS and treat it as a local issue.

Britain could keep a covert interest in the region through MI6 and MI5, pretending it’s not our problem even though 500 Brits are taking part in jihad in Syria and Iraq.

For: Would persuade extremist Muslims that Britain is not involving itself in Middle East issues, would save billions in defence funding and may encourage the region to sort out its own problems.

Against: Perilous to Britain as IS fighters could return to the UK ready to cause death and destruction. Also Britain must maintain an image of always being ready to fight against extremism.